Prenatal Diagnostic Testing for Genetic Conditions

Chorionic villus sampling and amniocentesis

Chorionic villus sampling (CVS) and amniocentesis are prenatal diagnostic tests that can provide detailed information about a baby’s chromosomes and DNA. Your care team might recommend these tests when there is an increased chance for a genetic condition during pregnancy. This might be based on family history, ultrasound findings or results from prenatal genetic screening.

At the Elizabeth J. Ferrell Fetal Health Center, our team offers both of these diagnostic procedures, along with comprehensive genetic counseling to help you understand the results. We will help you consider all your options and support you every step of the way.

Chorionic villus sampling (CVS)

CVS is a diagnostic procedure that collects a small sample of placental tissue, called chorionic villi, to evaluate a baby’s genetics. It is typically performed between 10 and 13 weeks of pregnancy, which allows families to receive information earlier in pregnancy.

The procedure can be done in one of two ways:

• Transcervical, through the cervix using a thin catheter (tube).
• Transabdominal, through the abdomen using a thin needle.

Your care team will choose the approach based on where your placenta is located and what is safest for you and your pregnancy. If you have twins or other multiples with their own placentas, your care team may need a sample from each placenta.

Risks and benefits of CVS

For families with a history of genetic or chromosomal concerns, CVS can help provide earlier answers and guide next steps in care. However, like many medical procedures, it does have some risks, such as bleeding, infection or pregnancy loss (about 1 in 500 cases). Your care team will talk with you about both the risks and the benefits of CVS so you can decide if it’s right for you.

Amniocentesis

Amniocentesis is a diagnostic procedure that involves collecting a small sample of amniotic fluid using a thin needle guided by ultrasound. It is usually performed at 15 weeks of pregnancy or later.

During the procedure, the clinician inserts a needle through the abdomen and into the amniotic sac. They will withdraw a small amount of fluid, which the genetics lab will analyze to look for certain genetic conditions. Your care team will explain the procedure in detail and answer any questions you may have.

Risks and benefits of amniocentesis

Amniotic fluid contains cells of the baby shed from the skin, respiratory system and urinary system. It can provide your care team with information about genetic disorders, congenital infections, and some other areas of potential concern. However, like many medical procedures, it does have some risks, such as cramping, bleeding or leaking of amniotic fluid, infection or preterm labor. Your care team will talk with you about both the risks and the benefits of amniocentesis so you can decide if it’s right for you.

Why would I need genetic tests like these?

Your care team may recommend CVS or amniocentesis if:

• A prenatal screening test, such as noninvasive prenatal testing (NIPT), shows an increased chance for a genetic condition.
• Ultrasound findings raise concern for an underlying genetic diagnosis.
• There is a known genetic condition in your family.
• You or your partner are carriers of a hereditary condition.
• A previous pregnancy was affected by a genetic or chromosomal condition.

What can CVS and amniocentesis diagnose?

These diagnostic tests can identify a range of genetic conditions, including:

• Chromosomal conditions, such as Down syndrome, trisomy 18 and trisomy 13.
• Microdeletions or microduplications, such as 22q11.2 deletion syndrome.
• Single-gene conditions, such as cystic fibrosis or sickle cell disease.

Genomic Answers for Kids (GA4K)

At Children’s Mercy, we are advancing the future of pediatric and prenatal care through innovative genomic research. The Genomic Answers for Kids (GA4K) program uses long-read genome sequencing to improve diagnostic rates for children and families affected by rare diseases.

Through GA4K, we are extending this cutting-edge technology into prenatal care to offer more comprehensive genetic information in pregnancies with congenital differences. Families who have an amniocentesis at the Fetal Health Center may be offered the opportunity to participate in this program.

As with all research opportunities, participation is completely voluntary and your medical care will not be affected by your decision about whether to participate.